sin(x+y)/sin(x-y)=m/n(sinxcosy+cosxsiny)/(sinxcosy-cosxsiny)=m/n上下同除以sinxcosy(1+tany/tanx)/(1-tany/tanx)=m/nn(1+tany/tanx)=m(1-tany/tanx)(m+n)tany/tanx=m-ntany/tanx=(m-n)/(m+n)